High frequency electronic devices

ABSTRACT

An electronic device wherein an interaction of an electron beam and a high frequency wave propagating through a delay line is achieved. The electron beam is made to strike substantially the whole length of said delay line simultaneously, which line upon this strike emits secondary electrons which are collected either by a grid parallel to the delay line or by the surface itself of said line. Such devices constituting either electronic amplifier or storage tubes.

United States Patent [1 1 Epsztein [451 July 31, 1973 1 HIGH FREQUENCYELECTRONIC DEVICES [75] Inventor: Bernard Epszteln, Paris, France [73]Assignee: Thomson-CSF, Paris, France [22] Filed: July 13, 1971 [21]Appl. No.: 162,112

[30] Foreign Application Priority Data July 30, 1970 France 7028232 [52]U.S. C1 330/43, 330/42, 330/44, 3l5/5.l2, 315/41 [51] Int. Cl. 03f 3/58[58] Field Of Search 315/393, 3, 4, 5, 315/6, 7, 41; 330/42, 43, 44

[56] References Cited UNITED STATES PATENTS 3,161,801 12/1964 Allen315/3 X 3,389,295 6/1968 Pietrzyk SIS/39.3

Primary Examiner-Nathan Kaufman Attorney-Edwin E. Greigg [57] ABSTRACTAn electronic device wherein an interaction of an electron beam and ahigh frequency wave propagating through a delay line is achieved. Theelectron beam is made to strike substantially the whole length of saiddelay line simultaneously, which line upon this strike emits'secondaryelectrons which are collected either by a grid parallel to the delayline or by the surface itself of said line.

Such devices constituting either electronic amplifier or storage tubes.

12 Claims, 5 Drawing Figures PATENTEU 1 3,750,043

SHEET 3 OF 3 1 HIGH FREQUENCY ELECTRONIC DEVICES The present inventionrelates to microwave electron tubes.

In this art the interaction between the electron beam and the electricfields generated by the wave in a structure parallel to the beam alongwhich the wave propagates is utilized when it is desired to amplify ordelay a microwave, for example in a traveling wave tube.

To provide for the interaction the wave velocity is reduced to a valuecomparable to that of the electrons of the beam by suitable selection ofthe delaying characteristics of the structure.

However, the microwave amplification of this type of mechanism issubject to limitations including the difficulties entailed in theefficient transfer of energy from the beam to the wave since the saidbeam and wave are geometrically separate in parallel planes.

The object of the present invention is to elimimate these difficulties.For this purpose the relative shifts of the beam and the wave arecontrolled in twoperpendicular directions so that all theelectromagnetic fields traveling along the delay line interactsimultaneously with the beam. In addition, an increase in the beamamplification results from the utilization of the secondary electronemission at the point of impingement of the beam on the delay line.

More specifically the invention relates to a microwave electron tubecomprising a wave delaying structure, an electron emission sourcedirecting electrons onto the longitudinal surface of the said structure,

means controlling the said emission, and coupling means injecting andejecting the waves propagating in the said structure, the secondaryemission ratio of the structure being greater than one when thestructure is exposed to the said electron emission.

The invention will be better understood from a consideration of theensuing description and by reference to the attached figures in whichFIG. 1 illustrates the assembly for one embodiment of an electronic tubein accordance with the invention FIG. 2 illustrates a detail of thistube FIG. 3 illustrates another embodiment of the tube of FIG. 1

FIG. 4 illustrates another electronic tube in accordance with theinvention and FIG. 5 illustrates an electronic tube in accordance withthe invention provided with several inputs and outputs.

Every kind of electronic tube in accordance with the invention anddescribed hereinafter comprises, as shown on FIG. 1 for example, withinan evacuated envelope schematically represented in E, an electron gun(I, 2, 3, 4) providing a wide electron beam (not shown) and a delay line5, of the interleaved kind for example, located opposite the electrongun in such a way that said line is bombarded by said electron beamsimulta neously onto the almost entirety of its length. A grid thepotential of which is positive relative to the cathode 1 accelerates theelectron beam towards the delay line 5. Said delay line 5 is connectedat one of its extremities to a coupling device 6 applying thereto themicrowave to be processed while a second device 7 connected to the otherextremity of said line picks up the processed wave.

current control electrode constituted by the grid 4.

Classical biasing means not represented are also provided.

Thus, the processing of a microwave injected to the delay line 5 by thecoupling device 6 is provided in accordance with the invention by anelectron beam striking said line simultaneously onto its whole effectivelength (except of course onto the coupling devices 6 and 7).

A convenient processing of said microwave, as concerning anamplification as well as concerning a delay as described hereinafter, isobtained in devices according to the invention with delay linesexhibiting the phenomenon of secondary electrons emission when bombardedby the electron beam emitted by the cathode 1. For this purpose, thedelay line 5 is either covered with a layer 8 of a material which willemit secondary electrons, or constituted by a material exhibiting itselfthis phenomenon, this depending on the embodiment considered.

In the embodiment illustrated by FIGS. 1 and 2, the delay line 5 isconstituted by an electric conductive material covered by a layer 8 ofan electric insulating material which is able of emitting secondaryelectrons when striked by the electron beam of the electron gun.

Furthermore, in the tube here represented where the processing of themicrowave injected by the coupling device 6 is an amplification, saidlayer 8 is covered with a thin film 9 of an electric conductivematerial.

This film 9 is provided to permit electrical charges to circulatethrough the delay line in such a way that the distribution of saidcharges being continuously leveled out onto the surface of the layer 8,the microwave to be processed may travel through the delay line. Thegrid 10 has very high positive potential in relation to the line 5 andcollects secondary electrons produced by layer 8 when said layer isstriked by the electron beam emitted by the electron gun of the device.The thickness of the film 9 is choosen to not disturb the passage ofsecondary electrons such produced.

The high frequency energy to be amplified is introduced at the input 6of the delay line and is propagated along same, creating between theelements thereof a system of moving electric and magnetic fields whichinduce in the conductive elements of said line an electric current whosevalue at any point is determined by that of the said fields at said samepoint.

Under these conditions, permanent electron bombardment of the delay lineis carried out. For this purpose, from its cathode l the electron-gunemits a beam of electrons which are focussed and guided by the electrode3, the intensity of the beam being regulated by the grid 4 and itsvelocity by the grid 10 the electrons strike the surface of the delayline after passing the grid 10. Under the impact of the incidentelectrons, the layer of material 8 emits secondary electrons which areimmediately attracted to and absorbed by the said grid. Potentials ofthe various electrodes of the tube and layers 8 and 9 (thickness andkind of material) are chosen so that the secondary emission operateswith a coefficient advantageoussly higher than unity and that secondaryelectrons thus emitted by layer 8 have energy enough to cross over thefilm 9, being afterwards catched by grid 10.

The distribution of the incident electrons is not uniform at the surfaceof the delay line in other words, because of the presence of theelectric fields propagating through the line, the incident electrons areattracted by zones corresponding to positive peaks in the travellingwave. Under the impact of said incident electrons said zones of layer 8emit secondary electrons absorbed by grid 10. Departure of saidsecondary electrons raises the corresponding zones of the delay line (ithas already been explained that these zones coincide with the positivepeaks in the travelling wave), to a still higher positive potential.

The amplitude of the positive peaks due to the microwave alone, isconsiderably increased by this mechanism of local augmenting of thepositive charges thus, the travelling microwave is amplified.

FIG. 3 illustrates another embodiment of an electronic tube inaccordance with the invention, differing from that of FIG. 1 solely interms of the type of delay line used.

Whereas the delay line of FIG. 1 is of the electrical delay type, thatof FIG. 3 is of the mechanical type. In accordance with a knownembodiment, it is constituted by a plate 11 of a piezoelectric materialprovided at its ends with two high frequency coupling devices.

' On this figure is only represented the beginning of the deviceenclosed in an envelope (not shown) for constituting a tube So, one cansee only the input coupling device (an equivalent output coupling devicebeing disposed identically at the end of said device). Said input Icoupling device comprises for example an input line 20 connected to thehigh frequency source (not shown) and passing through the plate 11 by ahole 21 and connected to a piece of an interleaved metallic line 12 laidon the surface of the plate 11 facing the electron gun (l, 2, 3, 4) insuch a way that said coupling device (20, 12) causes excitation of saidplate 11. In the embodiment here described said piece of line 11 is seton the plate 11 itself (it's the reason why it is represented by dashedlines) this piece ofline 11 might be set on layer 9 (not shown)providing that an electric isolation is realised between said piece 11and said layer 9.

In this embodiment, the delay is of mechanical origin and corresponds tothe reduced velocity at which an acoustic wave propagates through thepiezoelectric material, said wave being associated with the mechanicalstresses producedby the propagation of the electromagnetic wave ejectedthrough the input coupler (20, 12).

In accordance with the invention, said delay line is covered, as in thecase of FIGS. 1 and 2, with a layer 8 of a material which exhibits thesecondary emission phenomenon, and a thin film 9 of a conductivematerial. In some cases, the material of the plate 11 itself may exhibitthe secondary emission phenomenon the layer 8 is then superfluous andthe device is devoid of such a layer.

The operation of the device thus constituted is the same as that of theone already described in relation to FIGS. 1 and 2.

FIG. 4 illustrates a variant embodiment of the electronic tube inaccordance with the invention, in which the processing operated onto thehigh frequency signal injected to the delay line consists in stockingfor an arbitrary period of time an information which is a very shortportion of said high frequency signal.

This variant embodiment of a tube in accordance with the invention ishere described with atmechanical delay line constituted by a plate 11 ofa piezoelectric material as in FIG. 3. It is quite clear that such avariant which consists in a storage tube for stocking informations mayalso be realised with an electrical delay line as that one of FIG. 1 forexample.

Such storage tubes according to the invention are equivalent with regardto their general conception to the amplifier tubes described withreference to FIGS. 1 to 3. They only differ from said amplifier tubes bythe suppression of the conductive film 9 which was laid on layer 8 insaid tubes (FIGS. 2, 3) and by a different setting of the potential ofthe grid 10.

This absence of film 9 enables static charges to accumulate thusallowing the high frequency signal to be blocked in the manner describedhereinafter in the context of a piezoelectric delay line.

A very short high frequency signal is ejected in the form of a pulsethrough the input coupler of the delay line, electron emission from thegun being inhibited by the grid 4. When the pulse, in the form of a wavetrain of both electrical and mechanical nature is fully con tained onthe surface of the line, the grid 4 is used to unblock the electron-gun1 for a very short time, for example in the order of magnitude of, orless than, one quarter of the periodicity of the high frequency signal.

The potential of the second grid 10 is so adjusted relative to that oneof the delay line that the impactof the electrons emitted by saidelectron gun onto the surface of layer 8 liberates secondary electronsthe energy of which is such that they fall back onto the insulatingsurface of the piezoelectric material, concentrating at the regions ofpositive potential, that is to say where the wave peaks occur andremaining trapped there to thus form a permanent electrostatic image ofthe wave at the instantof bombardment these charge deposits createassociated permanent mechanical stresses inside the crystal.

An unblocking of the signal thus blocked onto the line may be achievedby unblocking the electron-gun under the control of the grid 4. Theelectron beam thus emitted gives rise to secondary electrons whichredistribute themselves onto the delay line at the locations which havebeen precedently depopulated of electrons, this having the effect oferasing the electrostatic and mechanical record obtained during theafore-described blocking period. This erasing cancels the electriccharges thus releasing the internal mechanical stresses and triggeringtwo surface waves which propagate in opposite directions. The one whichpropagates in the same direction as the initially injected wave in afaithful reconstitution of that wave and is picked up at the outputcoupler (not shown).

The tube in accordance with this embodiment of the invention thus makesit possible to arbitrarily delay a high frequency signal.

By way of example, the blocking or stocking time depends essentiallyupon the insulation of the structures utilised to conserve theelectrostatic charges and can range from some few microseconds toseveral months. The high frequency signal ranges between some fewmegacycles per second and some few, gigacycles per second the durationof the pulse can be as much as 50 microseconds and the input power isless than some watts.

FIG. 5 illustrates a variant embodiment of the invention, where theprovision of several input couplers 12, 13 and 14, and several outputcouplers (not shown), makes it possible to process several differentsignals onto several parts of the delay line.

FIG. 5 illustrates a tube where the processing realised is anamplification (see the presence of conductive film 9).

Such a variant embodiment may also concern storage tubes without film 9.

The electron beam 15 can then be selectively applied to one of thecorresponding parts of the delay line, this by the application ofsuitable potentials to the deflecting electrode 3 of the electron-gun,when a separate processing of said parts is wanted, or applied to thewhole delay line for a simultaneous processing of said parts.

This variant embodiment is described here with a mechanical delay lineit may also be realised with an electrical one.

What is claimed is 1. Electronic device providing an interaction betweena high frequency wave and an electron beam comprising within anevacuated envelope, an electron source delivering an adjustable electronbeam, a high frequency source delivering said high frequency wave, adelay line for propagating said wave, first coupling means for couplingsaid delay line to said high frequency source and constituting the inputof said device, second coupling means for extracting said wave from saiddelay line and constituting the output of said device, means foraccelerating said electron beam towards said delay line so that theelectrons of said beam strike simultaneously the whole effective lengthof said delay line, said delay line emitting secondary electrons uponsaid strike of said electron beam onto its surface, and means forcollecting said secondary electrons.

2. Electronic device according to claim 1 wherein said delay line ismade of an electric conductive material covered on its side striked bysaid electron beam with a material emitting secondary electrons uponsaid strike.

3. Electronic device according to claim 1 wherein said delay line ismade of a piezoelectric material.

4. Electronic device according to claim 3 wherein said piezoelectricmaterial emits secondary electrons upon said strike of said electronbeam.

5. Electronic device according to claim 3 wherein said piezoelectricmaterial is covered on its side striked by said electron beam with amaterial emitting secondary electrons upon said strike.

6. Electronic device according to claim 1 wherein said delay linecomprises several parts each one having its own said first'and secondcoupling means.

7. Electronic device according to claim 6 wherein means are provided todeflect said electron beam onto one or the other of said parts of saiddelay line.

8. Electronic device according to claim 1 wherein said means foraccelerating said electron beam towards said delay line comprise a gridlocated in the vicinity of said surface of said delay line striked bysaid electron beam and means for defining the potential of said grid ina positive way relative to said electron source.

9. Electronic device according to claim 8 wherein said potential of saidgrid is furthermore defined so as said grid constitute said means forcollecting said secondary electrons and wherein said surface of saiddelay line is covered with a thin film of an electric conductivematerial connected to means for defining its potential.

10. Electronic device according to claim 8 wherein said means forcollecting said secondary electrons is said surface of said delay linestriked by said electron beam.

11. Electronic tube for amplification of a high frequency signalcomprising an electronic device as claimed in claim 9, said tubeproviding amplification of said wave applied to said delay line.

12. Electronic tube for the storage of high frequency signals comprisingan electronic device as claimed in claim 10, said tube providing storageof high frequency signals the duration of which is less than, or equalto, the propagation time of said high frequency wave to proceed oversaid delay line.

1. Electronic device providing an interaction between a high frequencywave and an electron beam comprising within an evacuated envelope, anelectron source delivering an adjustable electron beam, a high frequencysource delivering said high frequency wave, a delay line for propagatingsaid wave, first coupling means for coupling said delay line to saidhigh frequency source and constituting the input of said device, secondcoupling means for extracting said wave from said delay line andconstituting the output of said device, means for accelerating saidelectron beam towards said delay line so that the electrons of said beamstrike simultaneously the whole effective length of said delay line,said delay line emitting seCondary electrons upon said strike of saidelectron beam onto its surface, and means for collecting said secondaryelectrons.
 2. Electronic device according to claim 1 wherein said delayline is made of an electric conductive material covered on its sidestriked by said electron beam with a material emitting secondaryelectrons upon said strike.
 3. Electronic device according to claim 1wherein said delay line is made of a piezoelectric material. 4.Electronic device according to claim 3 wherein said piezoelectricmaterial emits secondary electrons upon said strike of said electronbeam.
 5. Electronic device according to claim 3 wherein saidpiezoelectric material is covered on its side striked by said electronbeam with a material emitting secondary electrons upon said strike. 6.Electronic device according to claim 1 wherein said delay line comprisesseveral parts each one having its own said first and second couplingmeans.
 7. Electronic device according to claim 6 wherein means areprovided to deflect said electron beam onto one or the other of saidparts of said delay line.
 8. Electronic device according to claim 1wherein said means for accelerating said electron beam towards saiddelay line comprise a grid located in the vicinity of said surface ofsaid delay line striked by said electron beam and means for defining thepotential of said grid in a positive way relative to said electronsource.
 9. Electronic device according to claim 8 wherein said potentialof said grid is furthermore defined so as said grid constitute saidmeans for collecting said secondary electrons and wherein said surfaceof said delay line is covered with a thin film of an electric conductivematerial connected to means for defining its potential.
 10. Electronicdevice according to claim 8 wherein said means for collecting saidsecondary electrons is said surface of said delay line striked by saidelectron beam.
 11. Electronic tube for amplification of a high frequencysignal comprising an electronic device as claimed in claim 9, said tubeproviding amplification of said wave applied to said delay line. 12.Electronic tube for the storage of high frequency signals comprising anelectronic device as claimed in claim 10, said tube providing storage ofhigh frequency signals the duration of which is less than, or equal to,the propagation time of said high frequency wave to proceed over saiddelay line.